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Best would be share more details here first including whole Vin and you may get lucky.
Then, anyone Googling the Vin such as a current owner would find this thread also Members who have access to any databases can "quietly" add it to their Vin search lists...which are sometimes passed on to family/friends/others who may work for these groups and have the ability to periodically run batches of Vins through their systems.
Ask your own Insurance Co. if they have it in their system and if a hit, it's surprising even in today's privacy world what info someone may verbally tell you so have pen/paper ready.
Share more details of your connection to the car also when/where/what you know as this may offer more clues/leads/trails to follow.
Not that it may help find the car but great to see you already have GM Canada paperwork w/ as built RPO & other details.
As many here know, these are available for most '77 & newer GM vehicles regardless of where built or dealer location shipped to new.
SYC Members are second to none w/ connections also willingness to help plus it's amazing what fluky circumstances happen here sometimes that add up to success.
Best of luck w/ your quest!
~ Pete
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